PROJECT SUMMARY This project will provide multidisciplinary training for a dual-degree MD/PhD student in skin tissue engineering and burn reconstructive surgery, addressing an unmet clinical need for a skin substitute with full-regeneration potential. Burn injuries are a major clinical burden in the United States, with nearly 500,000 patients treated annually, a mortality rate of 4.9%, and an estimated cost of $2 billion per year. The standard of care for burn injuries includes autologous skin grafting, but these procedures require sufficient harvest sites that are scarce in patients with severe wounds. Tissue-engineered skin substitutes offer a promising alternative to skin grafts. However, current prototypes contain only up to two cell types; lack sweat and sebaceous glands, hair follicles, and pigmentation; and may not stimulate revascularization and innervation. Since the ultimate goal of a skin graft is to regenerate authentic anatomy and physiology of native skin, there is an immense need to develop bioengineered skin with more cell types and full regeneration potential. To meet the need for bioengineered skin, bioprinting techniques have been developed to more accurately engineer tissue substitutes with appropriate 3D structural organization. This proposal will test the hypothesis that a 3D bioprinted skin graft will support regeneration of native-like skin in full-thickness wounds in vivo, similar to skin autografts. To test this hypothesis, the fellowship applicant has proposed three Specific Aims. Aim 1 will delineate how bioprinted skin accelerates epidermal barrier formation in vivo. This aim will provide the applicant with training in digital planimetry analysis to measure rates of wound closure, and NOVATM dermal phase meter analysis to measure the extent of re-epithelialization over time. Aim 2 will explore how neovascularization occurs in bioprinted skin in vivo and will require competence qrtPCR to measure endothelial growth factors compared with IHC stained capillaries per mm2. Aim 3 will investigate how melanocyte migration impacts bioprinted skin pigmentation. This will require immunohistochemical staining to determine mouse vs. human tissue formation, hair follicle formation, and melanin production. The applicant has assembled a multidisciplinary team of sponsors, co- sponsors, contributors, and consultants with expertise in regenerative medicine, ECM imaging, biomaterials science, wound healing, dermatology, and burn reconstructive surgery. They have established a training plan with (1) Mentorship Meetings, (2) Coursework, (3) Research Training, and (4) Clinical Training that will allow the student to develop both technically and conceptually towards becoming an independent skin tissue engineer. This novel approach to treatment of full-thickness wounds, conducted at a world-class institute, will serve as a basis for the student's training, and allow this promising applicant to develop as a physician- scientist poised to address future deficits in burn reconstructive surgery through skin tissue engineering.